understood (present invisibly which She very well can ;-). In that case the sentence survives without any loss of meaning or grammatical vulnerability. I presume Shankara did not want to invoke ShAradA at every quarter pAda (for poetic reasons too!). Perhaps that is the unwritten rule in al...
' I could not understand this for a long time. But the other day, when I looked at the pine trees bending before the cold blasts from the mountain, I suddenly realized the meaning. You see, all the boughs, branches, twigs, and leaves simultaneously bend to the wind with tremendous vigor...